For assembling or combining two pieces of articles, a fastening device such as a screw is usually used. Generally, the fastening device can be dismantled by simply using a dismantling tool. For example, in a case that electronic appliance has got trouble or in views of curiosity about what is inside the electronic appliance, the user may personally detach the fastening device in order to examine the electronic components inside the electronic appliance. Since most users are often unfamiliar with the configuration and the circuitry of the electronic appliance, an incidental damage of the electronic appliance is possibly incurred. Moreover, the user may fail to reassemble the separated pieces of articles. If this electronic appliance is sent to the manufacturer offering the after-sales service, the serviceman may doubt whether the damage is naturally caused or man-made. Therefore, it is vital for the manufacturer to know if the product has not been altered since it left the manufacturer.
Take a power adapter for example. The power adapter usually comprises a first housing and a second housing coupled with each other. A closed space is defined between the first housing and the second housing for accommodating therein a printed circuit board. Conventionally, the first housing is coupled with the second housing via an ultrasonic welding technology or fastening a fastening device. Referring to FIG. 1, a schematic partial cross-sectional view of a conventional power adapter is illustrated. The first housing 11 is coupled with the second housing 12 via a fastening device 13. As shown in FIG. 1, the first housing 11 has a perforation 111. The second housing 12 has a groove 121 corresponding to the perforation 111 of the first housing 11. The groove 121 has an inner thread 122 formed on a portion of inner wall thereof. The fastening device 13 has a head portion 131 and a shaft portion 132. The shaft portion 132 has an external thread 133 wrapped around the free end thereof and mating with the inner thread 122 of the groove 121. For coupling the first housing 11 with the second housing 12, the shaft portion 132 of the fastening device 13 is penetrated through the perforation 111 of the first housing 11 and then screwed in the groove 121 such that the external thread 133 is engaged with the inner thread 122.
This mechanism of coupling the first housing 11 with the second housing 12 by the fastening device 13, however, has some drawbacks. For example, since the head portion 131 of the fastening device 13 is exposed outside the first housing 11, the user may personally detach the fastening device for examining the electronic components inside the power adapter by using a simple dismantling tool such as a screwdriver. In a case that the power adapter is sent to the manufacturer offering the after-sales service, the user and the serviceman may dispute whether the damage is naturally caused or man-made.
Therefore, there is a need to provide a tamper-evident mechanism for preventing the user from personally dismantling the fastening device.